Common electrode substrate and liquid crystal display device having the same

ABSTRACT

The present invention relates to a common electrode substrate that is opposed to an array substrate as well as to a liquid crystal display device having the substrate and provides a common electrode substrate capable of providing high luminance and good display characteristics as well as liquid crystal display device having such a common electrode substrate. A common electrode substrate is provided with a transparent insulating substrate to be arranged opposite to an array substrate having pixel electrodes formed in respective pixel regions that are defined by a plurality of gate bus lines and drain bus lines, and to hold a liquid crystal having negative dielectric anisotropy; a common electrode formed on the transparent insulating substrate; linear protrusions formed on the common electrode; and a light shield film formed on the transparent insulating substrate and having overlap regions that overlap portions of the pixel electrodes when viewed in the direction perpendicular to the surface of the transparent insulating substrate so as to shield, from light, alignment defective regions of the liquid crystal formed in regions of end portions of the pixel electrodes.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a common electrode substratethat is opposed to an array substrate as well as to a liquid crystaldisplay device having the substrate.

[0003] 2. Description of the Related Art

[0004] Liquid crystal display devices have a liquid crystal that issealed between a pair of substrates. Each of the paired substrates hasat least one electrode and an alignment film. TN (twisted nematic) modeliquid crystal display devices, which are widely used conventionally,have horizontal alignment films and a liquid crystal having positivedielectric anisotropy. Liquid crystal molecules are alignedapproximately parallel with the horizontal alignment film when novoltage is applied. Liquid crystal molecules rise so as to becomeapproximately perpendicular to the horizontal alignment film when avoltage is applied to those.

[0005] While TN mode liquid crystal display devices have such advantagesthat they can be made thin, they have a first disadvantage of a narrowviewing angle and a second disadvantage of low contrast. A method forsolving the first disadvantage and obtaining a wide viewing angle isdomain division. In the domain division, each pixel is divided into twodomains. In one domain, liquid crystal molecules rise or fall toward oneside. In the other domain, liquid crystal molecules rise or fall towardthe other side. By forming the domains having different view anglecharacteristics in each pixel, the view angle characteristic of thedevice as a whole is averaged, and a wide viewing angle can thereby beobtained.

[0006] A usual method for controlling the alignment of a liquid crystalis to rub an alignment film. In the case of the domain division, rubbingis performed in a first direction in one domain of each pixel by using amask, and then, rubbing is performed in a second direction that isopposite to the first direction in the other domain by using acomplementary mask. Alternatively, the entire alignment film is rubbedin a first direction, and then, one domain or the other domain of eachpixel is selectively irradiated with ultraviolet light by using a maskto produce a difference in the pre-tilt of liquid crystal moleculesbetween the one domain and the other domain.

[0007] Rubbing needs to be performed in liquid crystal display deviceshaving horizontal alignment films. Failures due to pollution and staticelectricity that occur during the rubbing are factors of lowering theyield.

[0008] On the other hand, in VA (vertically aligned) mode liquid crystaldisplay devices having vertical alignment films, liquid crystalmolecules are aligned approximately perpendicular to the verticalalignment films when no voltage is applied. Liquid crystal moleculesfall so as to become parallel with the vertical alignment films when avoltage is applied. This provides high contrast and solves the seconddisadvantage (low contrast) of the TN mode liquid crystal displaydevices. However, even in general VA mode liquid crystal display devicehaving vertical alignment films, the alignment films are usually rubbedto control the liquid crystal alignment.

[0009] Japanese Patent Application No. 185836/1998 of the presentapplicant proposes a liquid crystal display device in which the liquidcrystal alignment can be controlled without rubbing. This liquid crystaldisplay device is a VA mode liquid crystal display device havingvertical alignment films and negative dielectric anisotropy. To controlthe liquid crystal alignment, linear alignment regulating structures(protrusions or slits) are provided on each of paired substrates.

[0010] In this specification, this type of VA mode liquid crystaldisplay device will be hereinafter referred to as “MVA (multi-domainvertical alignment) liquid crystal display device.”

[0011] The MVA liquid crystal display device has advantages that therubbing is not necessary and domain division can be attained byarranging linear alignment regulating structures. Therefore, the MVAliquid crystal display device can provide a wide viewing angle and highcontrast. Since the rubbing is not necessary, the liquid crystal displaydevice can be manufactured easily and is free of pollution due to dust,etc. that would otherwise be scraped off alignment films during rubbing,leading to an increase of the reliability of the liquid crystal displaydevice.

[0012]FIG. 21 is a plan view showing the basic configuration of aconventional MVA liquid crystal display device and shows one pixel and aregion in its vicinity. This MVA liquid crystal display device is anactive matrix type liquid crystal display device in which each pixel isprovided with a thin-film transistor (TFT) 102 as a switching element.

[0013] Gate bus lines 104 extending in the right-left direction in FIG.21 and drain bus lines 106 extending in the top-bottom direction in FIG.21 are formed on an array substrate 122 that is provided with the TFTs102. Each TFT 102 is constructed of a drain electrode 108 that extendsfrom the drain bus line 106, a source electrode 110 that is opposed tothe drain electrode 108, and a portion (gate electrode) of the gate busline 104 which overlaps with the drain electrode 108 and the sourceelectrode 110. Although not shown in FIG. 21, channel layers made of,for example, an amorphous silicon (α-Si) film, are formed on therespective gate bus lines 104. The pixel electrodes 112 that areconnected to the respective source electrodes 110 are further formed onthe array substrate 122. Each pixel electrode 112 is provided with slits114 that are oblique with respect to the edges of the pixel electrode112. The slits 114 are alignment regulating structures on the arraysubstrate 122 side for controlling the liquid crystal alignment. Eachpixel electrode 112 is provided with connecting portions 116 so as notto be separated electrically by the slits 114. Thus, the pixel electrode112 in each pixel is electrically connected.

[0014] On a common electrode substrate 128 that is provided with acommon electrode and color filters (both not shown in FIG. 21) is formeda light shield film 136 (indicated by hatching in thetop-left-to-bottom-right direction) in the regions where the TFTs 102 onthe array substrate 122 are formed and other regions where neither thepixel electrodes 112 nor the alignment regulating structures (slits 114in FIG. 21) are formed. The light shield film 136 is formed to suppressleak current that is caused by light incident on the channel layer ofeach TFT 102, prevent leakage of light from the adjacent pixelelectrodes 112, and prevent color mixing between the adjacent pixels.For these reasons, the light shield film 136 is formed in such a mannerthat the edges approximately coincide with the edges of the pixelelectrodes 112 when viewed in the direction perpendicular to thesurfaces of the common electrode substrate 128. On the common electrodesubstrate 128 is also formed protrusions 118, which are the alignmentregulating structures together with the slits 114 that are formed on theopposite array substrate 122.

[0015] For example, in the case of an XGA liquid crystal display device(LCD panel) having a diagonal size of 15 inches, each pixel measures 99μm×297 μm. The width of the slits 114 and the protrusions 118 is 10 μm,and the interval between the slits 114 and the protrusions 118 is 25 μmwhen viewed in the direction parallel with the substrate surfaces.Further, the width of the connecting portions 116 of the pixelelectrodes 112 is 4 μm, and the distance between the end portions of thedrain bus lines 106 and the edges of the pixel electrodes 112 is 7 μm.

[0016] FIGS. 22 to 24, which are simplified sectional views taken alongline E-E in FIG. 21, show functions of the slits 114 and the protrusions118 that are the alignment regulating structures for controlling theliquid crystal alignment. FIG. 22 shows a state of the liquid crystalwhen no voltage is applied between the pair of substrates 122 and 128.In the array substrate 112 side, the pixel electrodes 112 are formed ona glass substrate 120, and the slits 114 are formed on the pixelelectrode 112. Moreover, an alignment film (vertical alignment film) 126is formed so as to cover the pixel electrodes 112 and the slits 114. Onthe other hand, in the common electrode substrate 128 side, the commonelectrode 124 is formed on the entire surface of the glass substrate 120so as to be opposed to the pixel electrodes 112. The protrusions 118made of an insulator (dielectric) such as a resist are formed on thecommon electrode 124. Moreover, an alignment film 126 is formed so as tocover the common electrode 124 and the protrusions 118.

[0017] A liquid crystal LC is sealed between the array substrate 122 andthe common electrode substrate 128. Liquid crystal molecules (indicatedby ellipses in FIG. 22) are aligned perpendicular to the alignment films126. Therefore, the liquid crystal molecules are also alignedperpendicular to the alignment films 126 which are formed on thesurfaces of the protrusions 118, and the liquid crystal molecules in thevicinity of the surfaces of the protrusions 118 are inclined against theglass substrate 120. However, strictly, the liquid crystal molecules inthe vicinity of the protrusions 118 are not aligned perpendicular to thealignment films 126. In the regions where the protrusions 118 are notformed, the liquid crystal molecules are aligned approximatelyperpendicular to the glass substrates 120 by the alignment films 126.Because of the continuity of the liquid crystal, the liquid crystalmolecules in the vicinity of the surface of each protrusion 118 followthe liquid crystal molecules located in the major part of the pixel, andhence, are inclined from the direction perpendicular to the alignmentfilm 126 toward the normal to the glass substrate 120. Although notshown in FIG. 22, a pair of polarizers are disposed outside the glasssubstrates 120 of the array substrate 122 and of the common electrodesubstrate 128 in the crossed Nicols state. Therefore, black display isobtained when no voltage is applied.

[0018]FIG. 23 shows equipotential lines when voltages are appliedbetween the electrodes of the pair of substrates. FIG. 24 shows a stateof the liquid crystal in this condition. As indicated by equipotentiallines (broken lines in FIG. 23), when voltages are applied between thepixel electrodes 112 and the common electrode 124, electric fielddistributions in the regions where the slits 114 or the protrusions 118are formed differ from those in the other regions. This is because ineach region where the slit 114 is formed, oblique electric fields areformed toward the common electrode 124 opposed from the end portions ofthe pixel electrode 112, and in each region where the protrusion 118 isformed, the electric field is distorted because the protrusion 118 is adielectric formed on the common electrode 124. Therefore, as shown inFIG. 24, liquid crystal molecules fall in directions indicated by arrowsin FIG. 24, that is, in such directions as to become perpendicular tothe electric field directions, in accordance with the magnitude of theelectric field. White display is thus obtained when voltages areapplied.

[0019] Where the linear protrusions 118 are formed in a linear state asshown in FIG. 21, the liquid crystal molecules in the vicinity of eachprotrusion 118 fall in two directions that are approximatelyperpendicular to the direction where the protrusion 118 is provided,with the protrusion 118 being as the boundary. Since liquid crystalmolecules in the vicinity of each protrusion 118 are slightly inclinedfrom the direction perpendicular to the glass substrate 120 even when novoltage is applied, they fall quickly in response to the electric field.Nearby the liquid crystal molecules also fall quickly following thebehavior of the liquid crystal molecules in the vicinity of theprotrusion 118 while being influenced by the electric field. Similarly,where the slits 114 are provided in a linear state as shown in FIG. 21,the liquid crystal molecules in the vicinity of each slit 114 fall intwo directions that are approximately perpendicular to the directionwhere the slit 114 is provided, with the slit 114 being as the boundary.

[0020] In this manner, in the region between two dash and dotted linesin FIG. 22, the liquid crystal molecules fall in the same direction,that is, they are aligned in the same direction. This is a region thatis denoted by symbol [A] in FIG. 21. As denoted by symbols [A] to [D] inFIG. 21 in a typified manner, in the MVA liquid crystal display device,the four regions having different alignment directions are formed ineach pixel, whereby a feature of a wide viewing angle is obtained. Theabove alignment control using the alignment regulating structures is notlimited to the case of the combinations of the slits 114 and theprotrusions 118 shown in FIGS. 21 to 24; a similar alignment control canbe performed by using, as the alignment regulating structures, thecombination of protrusions and protrusions or the combination of slitsand slits.

[0021] Although the MVA liquid crystal display device provides a wideviewing angle, it had a problem that there exist regions where thealignment of liquid crystal molecules is not stable, resulting inlowering the luminance. That is, when voltages are applied between theelectrodes, alignment defective regions 130 occur as hatched in FIG. 21.The alignment defective regions 130, where the light transmittance islow, are a factor of lowering the luminance in white display. Thealignment defective regions 130 occur along the drain bus lines 106 onthe side where the alignment regulating structures (protrusions 118 inFIG. 21) that are provided on the common electrode substrate 128 formobtuse angles with the edges of each pixel electrode 112 when viewed inthe direction perpendicular to the substrate surfaces. In the alignmentdefective regions 130, the liquid crystal molecules have differentalignment directions from the alignment directions that are controlledby the alignment regulating structures (protrusions 118 and slits 114 inFIG. 21) that are provided in the pair of substrates.

[0022]FIG. 25 is a plan view showing an MVA liquid crystal displaydevice that solves the above problem and, more specifically, shows onepixel and a region in its vicinity. The components in FIG. 25 having thesame functions as the corresponding components in FIG. 21 are given thesame reference symbols as the latter and will not be described below.The MVA liquid crystal display device of FIG. 25 has auxiliaryprotrusions 132 that are alignment regulating structures for performinga strong alignment control in the alignment defective regions 130 shownin FIG. 21. The auxiliary protrusions 132 branch off the protrusions 118and are formed along the end portions of each pixel electrode 112, thatis, the drain bus lines 106. By virtue of the auxiliary protrusions 132,liquid crystal molecules (indicated by cylinders in FIG. 25) a arealigned continuously with liquid crystal molecules b, whereby thealignment of liquid crystal molecules is made stable in the alignmentdefective regions 130.

[0023]FIG. 26 shows a display area in which a band-like black figurethat is long in the top-bottom direction in FIG. 26 (hereinafterreferred to as “black vertical band”) is displayed against a whitebackground on the conventional MVA liquid crystal display device of FIG.25. In a display area 134, pixel A that is part of the backgrounddisplays white, and pixel B in the black vertical band displays black.Although pixel C that is located under the black vertical band in FIG.26 displays white, it is darker than pixel A. Pixel C becomes moredarker than pixel A as the black vertical band becomes longer in thevertical direction in FIG. 26. As described above, the conventional MVAliquid crystal display device of FIG. 25 has the problem that when ablack vertical band is displayed against a white background, a regiondisplaying white under the black vertical band is displayed darker thanthe other region displaying white.

[0024] Similarly, FIG. 27 shows a display area in which a band-likewhite figure that is long in the top-bottom direction in FIG. 26(hereinafter referred to as “white vertical band”) is displayed againsta black background on the conventional MVA liquid crystal display deviceof FIG. 25. In the display area 134, pixel A that is part of thebackground displays black, and pixel B in the white vertical banddisplays white. Although pixel C that is located under the whitevertical band in FIG. 26 displays black, it is brighter than pixel A.Pixel C becomes more brighter than pixel A as the white vertical bandbecomes longer in the vertical direction in FIG. 26. As described above,the conventional MVA liquid crystal display device of FIG. 25 has theproblem that when a white vertical band is displayed against a blackbackground, a region displaying black under the white vertical band isdisplayed brighter than the other region displaying black. In thefollowing, the above-described phenomenon that pixel C and its vicinitybecome brighter or darker than pixel A and its vicinity will be referredto as “vertical crosstalk.” The vertical crosstalk occurs in such amanner that horizontal electric fields that develop between the drainbus lines 106 and end portions of each pixel electrode 112 where theauxiliary protrusions 132 are not formed influence the alignment ofliquid crystal molecules.

SUMMARY OF THE INVENTION

[0025] An object of the present invention is to provide a commonelectrode substrate capable of providing high luminance and good displaycharacteristics as well as a liquid crystal display device having such acommon electrode substrate.

[0026] The above object is attained by a common electrode substratecomprising a transparent insulating substrate to be arranged opposite toan array substrate having pixel electrodes formed in respective pixelregions that are defined by a plurality of gate bus lines and drain buslines, and to hold a liquid crystal having negative dielectricanisotropy; a common electrode formed on the transparent insulatingsubstrate; alignment regulating structures having linear protrusionsformed on the common electrode; and a light shield film formed on thetransparent insulating substrate and having overlap regions that overlapthe pixel electrodes when viewed in the direction perpendicular to thesurface of the transparent insulating substrate so as to shield, fromlight, alignment defective regions of the liquid crystal formed inregions of end portions of the pixel electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIGS. 1 to 3 are graphs for description of the main reason forvertical crosstalk that occurs in a conventional liquid crystal displaydevice as a basis of a first embodiment of the present invention;

[0028]FIGS. 4 and 5 are schematic sectional views for description of themain reason for the vertical crosstalk that occurs in the conventionalliquid crystal display device as a basis of the first embodiment of theinvention;

[0029]FIG. 6 is a plan view showing the configuration of theconventional liquid crystal display device as a basis of the firstembodiment of the invention;

[0030] FIGS. 7 to 9 are graphs for description of the main reason forvertical crosstalk that occurs in the conventional liquid crystaldisplay device as a basis of a first embodiment of the presentinvention;

[0031]FIGS. 10 and 11 are schematic sectional views for description ofthe main reason for the vertical crosstalk that occurs in theconventional liquid crystal display device as a basis of the firstembodiment of the invention;

[0032]FIG. 12 shows the entire configuration of a liquid crystal displaydevice according to the first embodiment of the invention;

[0033]FIG. 13 is a plan view showing a common electrode substrateaccording to the first embodiment of the invention;

[0034]FIG. 14 is a graph showing a relationship between the effect andthe overlap width of overlap regions of a light shield film as measuredfrom the end portions of a pixel electrode;

[0035]FIG. 15 is a graph showing a relationship between the paneltransmittance and the overlap width of the overlap regions of the lightshield film as measured from the edges of the pixel electrode;

[0036]FIG. 16 is a plan view showing a common electrode substrateaccording to a modification of the first embodiment of the invention;

[0037]FIGS. 17 and 18 are schematic sectional views showing the commonelectrode substrate according to the modification of the firstembodiment;

[0038]FIG. 19 is a plan view showing a common electrode substrateaccording to a second embodiment of the invention;

[0039]FIG. 20 is a schematic sectional view showing the common electrodesubstrate according to the second embodiment of the invention;

[0040]FIG. 21 is a plan view showing the configuration of a conventionalliquid crystal display device;

[0041] FIGS. 22 to 24 are schematic sectional views showing theconfiguration of the conventional liquid crystal display device of FIG.21;

[0042]FIG. 25 is a plan view showing the configuration of anotherconventional liquid crystal display device; and

[0043]FIGS. 26 and 27 illustrate a problem of the conventional liquidcrystal display device of FIG. 25.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] A common electrode substrate and a liquid crystal display devicehaving the substrate according to a first embodiment of the presentinvention will be hereinafter described with reference to FIGS. 1 to 18.First, the main reason for the vertical crosstalk that occurs in theconventional MVA liquid crystal display device as a basis of the firstembodiment of the invention will be described with reference to FIGS. 1to 11. FIGS. 1 to 3 are graphs showing examples of a gate voltage, adrain voltage, a pixel voltage, and a common voltage in pixels A, B, andC shown in FIG. 26, respectively. FIG. 1 shows a gate voltage V_(g), adrain voltage V_(d), a pixel voltage V_(p), and a common voltage V_(com)in pixel A. The abscissa represents the time and covers about two frames(e.g., about {fraction (1/30)} sec) in FIG. 1. The ordinate representsthe voltage (V). In FIG. 26, all the pixels on the drain bus lineincluding pixel A display white. Therefore, the drain voltage V_(d)becomes +5 V or −5 V every frame cycle. When the gate voltage V_(g) isapplied to the gate electrode, +5 V or −5 V of the drain voltage V_(d)is written to pixel A as the pixel voltage V_(p). The pixel voltageV_(p) is held until the next frame by a storage capacitor (not shown).In this example, the common voltage V_(com) is always equal to 0 V. Thepotential difference e between the pixel voltage V_(p) and the drainvoltage V_(d) is equal to 10 V in most of each frame period.

[0045]FIG. 2 shows a gate voltage V_(g), a drain voltage V_(d), a pixelvoltage V_(p), and a common voltage V_(com) in pixel B shown in FIG. 26.The abscissa of FIG. 2, which represents the time, is the same as thatof FIG. 1 and covers about two frames. The ordinate represents thevoltage (V). Pixel B displays black, and in FIG. 26 most of the pixelson the drain bus line including pixel B also display black. Therefore,the drain voltage V_(d) is equal to +1 V or −1 V in most of each frameperiod and is equal to +5 V or −5 V in the other periods. When the gatevoltage V_(g) is applied to the gate electrode, +1 V or −1 V of thedrain voltage V_(d) is written to pixel B as the pixel voltage V_(p).

[0046]FIG. 3 shows a gate voltage V_(g), a drain voltage V_(d), a pixelvoltage V_(p), and a common voltage V_(com) in pixel C shown in FIG. 26.The abscissa of FIG. 3 represents the time and covers about two framesas in the cases of FIGS. 1 and 2. The ordinate represents the voltage(V). Although pixel C displays white, in FIG. 26 most of the pixels onthe drain bus line including pixel C display black. Therefore, the drainvoltage V_(d) is equal to +1 V or −1 V in most of each frame period andis equal to +5 V or −5 V in the other periods. The period when the drainvoltage V_(d) is equal to +1 V or −1 V increases in proportion to thevertical length of the black vertical band. When the gate voltage V_(g)is applied to the gate electrode, +5 V or −5 V of the drain voltageV_(d) is written to pixel C as the pixel voltage V_(p). The potentialdifference e between the pixel voltage V_(p) and the drain voltage V_(d)is equal to 6 V in most of each frame period and is equal to 10 V inother periods. The actual potential difference e between the pixelelectrode and the drain bus line is equal to an average value of them.The actual potential difference e is approximately equal to 6 V if thevertical length of the black vertical band is long.

[0047] The states of liquid crystal molecules in pixel A and pixel Cwill be described below with reference to FIGS. 4 to 6. FIG. 4 is aschematic sectional view of an end portion of a pixel electrode 16 ofpixel A along a drain bus line 42. An array substrate 32 has the drainbus line 42 and the pixel electrode 16 on a glass substrate 22. A commonelectrode 34 that is opposed to the array substrate 32 has a lightshield film 6 that is generally formed in a region where the pixelelectrode 16 is not formed, and a common electrode 24 that is formed onthe almost entire surface of the substrate. Vertical alignment films(not shown) for orienting liquid crystal molecules perpendicular to thetwo substrates 32 and 34 when no voltage is applied are formed on theopposite surfaces of the two substrates 32 and 34, respectively. Aliquid crystal LC having negative dielectric anisotropy is sealedbetween the two substrates 32 and 34. Many of the liquid crystalmolecules are inclined rightward in FIG. 4 by the electric field betweenthe pixel electrodes 16 and the common electrode 24, whereby a whitedisplay is obtained in pixel A.

[0048] As shown in FIG. 1, in pixel A, the drain voltage V_(d) of thedrain bus line 42 becomes +5 V or −5 V every frame cycle, and the pixelvoltage V_(p) of the pixel electrode 16 is equal to −5 V or +5 V. Thecommon voltage V_(com) of the common electrode 24 is equal to 0 V.Therefore, the potential difference between the pixel electrode 16 andthe drain bus line 42 is approximately equal to 10 V, and the potentialdifference between the pixel electrode 16 and the common electrode 24 isequal to 5 V. Broken lines in FIG. 4 indicate electric fields E₁ and E₂that develop between the electrodes, and a relationship |E₂|>E₁| holds.That is, the horizontal electric field E₂ that is stronger than theelectric field E₁ between the pixel electrode 16 and the commonelectrode 24 develops between the pixel electrode 16 and the drain busline 42.

[0049] Influenced by the strong horizontal electric field E₂, the liquidcrystal molecules between the pixel electrode 16 and the drain bus line42 are aligned approximately perpendicular to the surfaces of the twosubstrates 32 and 34. However, since the light shield film 6 shieldsfrom light the region from the drain bus line 42 to the end portion ofthe pixel electrode 16, the alignment defect in this region does notaffect the display. Further, although the liquid crystal molecules inthe end portion of the pixel electrode 16 are inclined being influencedby the horizontal electric field E₂, this is not problematic because itdisplays white originally.

[0050]FIG. 5 is a schematic sectional view of an end portion of thepixel electrode 16 of pixel C extending along the drain bus line 42. Thecomponents in FIG. 5 having the same functions as the correspondingcomponents in FIG. 4 are given the same reference symbols as the latterand will not be described below. As in the case of pixel A shown in FIG.4, many of the liquid crystal molecules are inclined rightward in FIG. 5by the electric field between the pixel electrode 16 and the commonelectrode 24, whereby a substantially white display is obtained in pixelC.

[0051] As shown in FIG. 3, in pixel C, the drain voltage V_(d) of thedrain bus line 42 is equal to +1 V or −1 V in most of each frame period,and the pixel voltage V_(d) of the pixel electrode 16 is equal to +5 Vor −5 V. The common voltage V_(com) of the common electrode 24 is equalto 0 V. Therefore, the potential difference e between the pixelelectrode 16 and the drain bus line 42 is approximately equal to 6 V,and the potential difference between the pixel electrode 16 and thecommon electrode 24 is equal to 5 V. Broken lines in FIG. 5 indicateelectric fields E₁ and E₂ that develop between the electrodes, and arelationship |E₂|≅|E₁| holds. That is, the horizontal electric field E₂that is approximately as strong as the electric field El between thepixel electrode 16 and the common electrode 24 develops between thepixel electrode 16 and the drain bus line 42.

[0052] Influenced by the horizontal electric field E₂, the liquidcrystal molecules between the pixel electrode 16 and the drain bus line42 are aligned approximately perpendicular to the surfaces of the twosubstrates 32 and 34. However, since the light shield film 6 shieldsfrom light the region from the drain bus line 42 to the end portion ofthe pixel electrode 16, the alignment defect in this region does notaffect the display. The liquid crystal molecules in the end portion ofthe pixel electrode 16 are not inclined sufficiently because they areinfluenced by the horizontal electric field E₂ that is approximately asstrong as the electric field E₁ that is perpendicular to the twosubstrates 32 and 34. As a result, in the end portion of the pixelelectrode 16, the transmission light quantity is smaller than in theother portion of the same pixel, and hence, pixel C is displayed darkerthan pixel A; vertical crosstalk occurs. FIG. 6 is a plan view, similarto FIG. 25, of one pixel of the liquid crystal display device wherevertical crosstalk occurs. Alignment defective regions 56 where theabove-described alignment defect occurs are regions that correspond toend portions of the pixel electrode 112 extending along the drain buslines 106 and where the auxiliary protrusions 132 are not formed.

[0053] FIGS. 7 to 9 are graphs showing examples of a gate voltage, adrain voltage, a pixel voltage, and a common voltage in pixels A, B, andC shown in FIG. 27, respectively. FIGS. 7 to 9 are similar to FIGS. 1 to3, and the abscissa represents the time and covers about two frames. Theordinate represents the voltage (V). FIG. 7 shows a gate voltage V_(g),a drain voltage V_(d), a pixel voltage V_(p), and a common voltageV_(com) in pixel A. In FIG. 7, since all the pixels on the drain busline 42 including pixel A display black, the drain voltage V_(d) becomes+1 V or −1 V every frame cycle. When the gate voltage V_(g) is appliedto the gate electrode, +1 V or −1 V of the drain voltage V_(d) iswritten to pixel A as the pixel voltage V_(p). The potential differencee between the pixel voltage V_(p) and the drain voltage V_(d) is equalto 2 V in most of each frame period.

[0054]FIG. 8 shows a gate voltage V_(g), a drain voltage V_(d), a pixelvoltage V_(p), and a common voltage V_(com) in pixel B shown in FIG. 27.Pixel B displays white. In FIG. 8, since most of the pixels on the drainbus line 42 including pixel B also display white, the drain voltageV_(d) is equal to +5 V or −5 V in most of each frame period and is equalto +1 V or −1 V in the other periods. When the gate voltage V_(g) isapplied to the gate electrode, +5 V or −5 V of the drain voltage V_(d)is written to pixel B as the pixel voltage V_(p).

[0055]FIG. 9 shows a gate voltage V_(g), a drain voltage V_(d), a pixelvoltage V_(p), and a common voltage V_(com) in pixel C shown in FIG. 27.Although pixel C displays black, in FIG. 27 most of the pixels on thedrain bus line 42 including pixel C display white. Therefore, the drainvoltage V_(d) is equal to +5 V or −5 V in most of each frame period andis equal to +1 V or −1 V in the other periods. The period when the drainvoltage V_(d) is equal to +5 V or −5 V increases in proportion to thevertical length of the white vertical band. When the gate voltage V_(g)is applied to the gate electrode, +1 V or −1 V of the drain voltageV_(d) is written to pixel C as the pixel voltage V_(p). The potentialdifference e occurred between the pixel voltage V_(p) and the drainvoltage V_(d) is equal to 6 V in most of each frame period and is equalto 2 V in other periods. The actual potential difference e between thepixel electrode 16 and the drain bus line 42 is equal to an averagevalue of them. The actual potential difference e is approximately equalto 6 V if the vertical length of the white vertical band is long.

[0056] The states of liquid crystal molecules in pixel A and pixel Cwill be described below with reference to FIGS. 10 and 11. FIG. 10 is aschematic sectional view of an end portion of the pixel electrode 16 ofpixel A extending along the drain bus line 42. The components in FIG. 10having the same functions as the corresponding components in FIG. 4 aregiven the same reference symbols as the latter and will not be describedbelow. When no voltage is applied, liquid crystal molecules are alignedapproximately perpendicular to the two substrates 32 and 34 by thevertical alignment films (not shown), whereby a black display isobtained in pixel A.

[0057] As shown in FIG. 7, in pixel A, the drain voltage V_(d) of thedrain bus line 42 becomes +1 V or −1 V every frame cycle, and the pixelvoltage V_(p) of the pixel electrode 16 is equal to −1 V or +1 V. Thecommon voltage V_(com) of the common electrode 24 is equal to 0 V.Therefore, the potential difference e between the pixel electrode 16 andthe drain bus line 42 is approximately equal to 2 V, and the potentialdifference between the pixel electrode 16 and the common electrode 24 isequal to 1 V. A broken line in FIG. 10 indicates an electric field E₂that develops between the electrodes. No horizontal electric field thatis stronger than the electric field between the pixel electrode 16 andthe common electrode 24 develops between the pixel electrode 16 and thedrain bus line 42.

[0058]FIG. 11 is a schematic sectional view of an end portion of thepixel electrode 16 of pixel C extending along the drain bus line 42. Thecomponents in FIG. 11 having the same functions as the correspondingcomponents in FIG. 4 are given the same reference symbols as the latterand will not be described below. As in the case of pixel A shown in FIG.10, many of the liquid crystal molecules are aligned approximatelyperpendicular to the two substrates 32 and 34 by the vertical alignmentfilms, whereby pixel C displays substantially black.

[0059] As shown in FIG. 9, in pixel C, the drain voltage V_(d) of thedrain bus line 42 is equal to +5 V or −5 V in most of each frame period,and the pixel voltage V_(p) of the pixel electrode 16 is equal to +1 Vor −1 V. The common voltage V_(com) of the common electrode 24 is equalto 0 V. Therefore, the potential difference e between the pixelelectrode 16 and the drain bus line 42 is approximately equal to 6 V,and the potential difference between the pixel electrode 16 and thecommon electrode 24 is equal to 1 V. The potential difference betweenthe drain bus line 42 and the common electrode 24 is equal to 5 V.Broken lines in FIG. 11 indicate electric fields E₂ and E₃ that developbetween the electrodes. The horizontal electric field E₂ that isstronger than the electric field between the pixel electrode 16 and thecommon electrode 24 develops between the pixel electrode 16 and thedrain bus line 42. Also, the strong electric field E₃ also developsbetween the drain bus line 42 and the common electrode 24.

[0060] Influenced by the horizontal electric field E₂ between the pixelelectrode 16 and the drain bus line 42 and the electric field E₃ betweenthe drain bus line 42 and the common electrode 24, the liquid crystalmolecules over the end portion of the pixel electrode 16 are inclinedrightward in FIG. 11. This alignment defect causes light leakage in theend portion of the pixel electrode 16, as a result of which pixel C isdisplayed brighter than pixel A, whereby vertical crosstalk occurs. Thisalignment defect occurs in the alignment defective regions 56 shown inFIG. 6.

[0061] The schematic configuration of a common electrode substrate and aliquid crystal display device having the substrate according to thefirst embodiment will be outlined with reference to FIGS. 12 and 13.FIG. 12 shows the entire configuration of the liquid crystal displaydevice according to the first embodiment. A display area 86 in which anumber of pixel regions 84 each having a TFT 2, a storage capacitor 4,and a pixel electrode that is a transparent conductive film made of, forexample, indium tin oxide (ITO) are arranged in a matrix form is definedon an array substrate 32. In FIG. 12, an equivalent circuitcorresponding to one pixel of the liquid crystal display device is shownin the pixel region 84. Agate bus line driving circuit 88 is disposed onthe left in the surrounding of the display area 86, and a drain bus linedriving circuit 90 is disposed in the upper portion of FIG. 12. Inputterminals 92 for receiving a dot clock signal, a horizontal synchronoussignal (Hsync), a vertical synchronous signal (Vsync), and RGB data fromthe system side are provided at a panel top portion (see FIG. 12).

[0062] The array substrate 32 is opposed to and attached to a commonelectrode substrate 34 via a sealing agent (not shown). A liquid crystalLC having negative dielectric anisotropy is sealed in a cell gap formedbetween the array substrate 32 and the common electrode substrate 34.Each pixel electrode on the array substrate 32, the common electrode onthe common electrode substrate 34, and the liquid crystal LC interposedtherebetween form a liquid crystal capacitor LC. On the other hand, adisplay electrode and a storage capacitor bus line that are formed inthe array substrate 32 side form a storage capacitor 4.

[0063] In the display area 86, a plurality of drain bus lines 42extending in the top-bottom direction in FIG. 12 are arranged parallelwith each other in the right-left direction in FIG. 12. The plurality ofdrain bus lines 42 are each connected to the drain bus line drivingcircuit 90, and prescribed gradation voltages are applied to therespective drain bus lines 42.

[0064] A plurality of gate bus lines 36 extending in a directionapproximately perpendicular to the drain bus lines 42 are arrangedparallel with each other in the top-bottom direction in FIG. 12. Theplurality of gate bus lines 36 are each connected to the gate bus linedriving circuit 88. The gate bus line driving circuit 88 outputs gatepulses sequentially to the plurality of gate bus lines 36 in synchronismwith bit outputs that are output from a built-in shift register.

[0065] When a gate pulse is output from the gate bus line drivingcircuit 88 to one of the plurality of gate bus lines 36, the pluralityof TFTs 2 connected to the gate bus line 36 are turned on. As a result,gradation voltages being applied from the drain bus line driving circuit90 to the drain bus lines 42 are applied to the respective pixelelectrodes.

[0066]FIG. 13 is a plan view showing the configurations of the commonelectrode substrate and the liquid crystal display device having thesubstrate according to the first embodiment. FIG. 13 shows one pixel ofthe liquid crystal display device. The gate bus lines 42 extending inthe right-left direction in FIG. 13 and the drain bus lines 36 extendingin the top-bottom direction in FIG. 13 are formed on the array substrate32 that is provided with the TFTs 2. Each TFT 2 is composed of a drainelectrode 52 that extends from the drain bus line 42, a source electrode54 that is arranged opposite to the drain electrode 52, and a portion(gate electrode) of the gate bus line 36 which overlaps with the drainelectrode 52 and the source electrode 54. Although not shown in FIG. 13,channel layers that are amorphous silicon (α-Si) films, for example, areformed on the respective gate bus lines 36. The pixel electrodes 16 thatare connected to the respective source electrodes 54 are further formedon the array substrate 32. Each pixel electrode 16 is provided withslits 12 that are oblique with respect to the edges of the pixelelectrode 16. The slits 12 are alignment regulating structures on thearray substrate 32 side for controlling the liquid crystal alignment.Each pixel electrode 16 has connecting portions 14 so as not to beseparated electrically by the slits 12, whereby the pixel electrode 16in each pixel is electrically connected. FIG. 13 does not show a storagecapacitor bus line that traverses the pixel at the center.

[0067] The common electrode and color filters (both not shown in FIG.13) are formed on the common electrode substrate 34. A light shield film6 (indicated by hatching; made of a metal such as Cr) is formed in theregions where the TFTs 2 are formed on the array substrate 32 and otherregions where neither the pixel electrodes 16 nor the alignmentregulating structures (slits 12 in FIG. 13) are formed. The light shieldfilm 6 is formed in such a manner that the edges approximately coincidewith the edges of the pixel electrodes 16 when viewed in the directionperpendicular to the surfaces of the common electrode substrate 34. Onthe common electrode substrate 34, linear protrusions 8 as alignmentregulating structures are formed so as to be oblique with respect to theedges of the pixel electrode 16. Auxiliary protrusions 10 as alignmentregulating structures are formed so as to branch off the protrusions 8and extend along those portions of the drain bus lines 42 which areopposed to end portions of the pixel electrode 16. The light shield film6 has overlap regions 18 that coextend with those portions of the pixelelectrode 16 which extend along the drain bus lines 42 and where theauxiliary protrusions 10 are not formed, when viewed in the directionperpendicular to the surfaces of the common electrode substrate 34. Theoverlap regions 18 are formed so as to shield from light the alignmentdefective regions 56 that occur in the regions of the end portions ofthe pixel electrode 16.

[0068]FIG. 14 is a graph showing a relationship between the shieldeffect and the width of the overlap regions 18 provided on the lightshield film 6. The abscissa represents the width (in μm) of the overlapregions 18, and the ordinate represents the degree of crosstalk in termsof the easiness of recognition of a difference in brightness betweenpixels C and A shown in FIG. 26 or 27. The width of the overlap regions18 is the distance between the edges of the overlap regions 18 extendingalong the direction of the drain bus lines 42 and the edges of the pixelelectrodes 16 in the direction of the drain bus lines 42 when viewed inthe direction perpendicular to the substrate surface. As shown in FIG.14, when the width of the overlap regions 18 is 2 μm or less, adifference in brightness is recognizable, which means occurrence ofvertical crosstalk. When the width of the overlap regions 18 is 4 μm, adifference in brightness is barely recognizable, which means occurrenceof vertical crosstalk. When the width of the overlap regions 18 is 6 μmor more, a difference in brightness is not recognizable, which meansabsence of vertical crosstalk. Therefore, the vertical crosstalk can beprevented by making the width of the overlap regions 18 greater than orequal to 2 μm when viewed in the direction perpendicular to thesubstrate surface, the effect of preventing the vertical crosstalk canbe obtained.

[0069]FIG. 15 is a graph showing a relationship between the paneltransmittance and the width of the overlap regions 18 of the lightshield film 6. The abscissa represents the width (in μm) of the overlapregions 18, and the ordinate represents the panel transmittance (in %).As shown in FIG. 15, when the width of the overlap regions 18 is 0 μm(i.e., no overlap regions 18 exist), the panel transmittance is 5.0%.The panel transmittance decreases as the width of the overlap regions 18increases. When the width of the overlap regions 18 is 12 μm, the paneltransmittance is 4.0%. Therefore, to secure the panel transmittance of4.0% or more, the width of the overlap regions 18 should be 12 μm orless when viewed in the direction perpendicular to the substratesurface.

[0070] According to the first embodiment, the vertical crosstalk can beprevented by shielding from light the alignment defective regions 56with the overlap regions 18 of the light shield film 6.

[0071] Next, a common electrode substrate according to a modification ofthe first embodiment will be described with reference to FIGS. 16 to 18.FIG. 16 is a plan view showing the shape of a light shield film 6 of thecommon electrode substrate 34 according to the modification of the firstembodiment. The components in FIG. 16 having the same functions as thecorresponding components in FIG. 13 are given the same reference symbolsas the latter and will not be described below. This modification ischaracterized in that the light shield film 6 is formed outside thepixel electrode 16 when viewed in the direction perpendicular to thesurface of the common electrode substrate 34 in the normal alignmentregions where the auxiliary protrusions 10 are formed. In FIG. 16, edges19 of the light shield film 6 in the regions where the auxiliaryprotrusions 10 are formed are located outside hidden lines representingedges 20 of the pixel electrode that are drawn in the auxiliaryprotrusions 10.

[0072]FIG. 17 is a schematic sectional view taken along line D-D in FIG.16. The array substrate 32 has an insulating film 30 that is formed onthe glass substrate 22 as a transparent insulating substrate. The drainbus line 42 is formed on the insulating film 30 on the right side inFIG. 17. A protective film 28 is formed over the entire array substrate32 on the drain bus line 42. The pixel electrode 16 is formed on theprotective film 28 on the left side in FIG. 17.

[0073] On the other hand, the common electrode substrate 34 that isopposed to the array substrate 32 has the light shield film 6 that isformed on the glass substrate 22. The light shield film 6 has theoverlap region 18 that coextends with the right end portion (see FIG.17) of the pixel electrode 16 when viewed in the direction perpendicularto the surface of the common electrode substrate 34. Color filters 26are formed on the light shield film 6. The common electrode 24 is formedover the entire common electrode substrate 34 on the color filters 26.

[0074]FIG. 18 is a schematic sectional view taken along line E-E in FIG.16. The components in FIG. 18 having the same functions as thecorresponding components in FIG. 17 are given the same reference symbolsas the latter and will not described below. FIG. 18 shows a normalalignment region where the auxiliary protrusion 10 is formed on thecommon electrode 24 at such a position as to be opposed to the endportion of the pixel electrode 16. The light shield film 6 is formedoutside the pixel electrode 16 when viewed in the directionperpendicular to the surface of the common electrode substrate 34.

[0075] To prevent reflection due to exposure of the surfaces of thedrain bus lines 42, it is desirable that the distance between the endportions 19 of the light shield film 6 and the end portions 20 of thepixel electrode 16, when viewed parallel with the surface of the commonelectrode substrate 34, be smaller than or equal to the distance (e.g.,7 μm) between the pixel electrode 16 and the drain bus lines 42.

[0076] Since the auxiliary protrusions 10 formed on the common electrodesubstrate 34 strongly restrict the orientation of liquid crystalmolecules, no alignment defect occurs in the regions where the auxiliaryprotrusions 10 are formed. Therefore, the aperture ratio can beincreased by aligning the light shield film 6 outside the pixelelectrode between when viewed in the direction perpendicular to thesurface of the common electrode substrate 34 in the regions where theauxiliary protrusions 10 are formed. Therefore, this modification canprovide the same advantage as in the first embodiment, withoutdecreasing the panel transmittance.

[0077] Next, a common electrode substrate and a liquid crystal displaydevice having the substrate according to a second embodiment of theinvention will be described with reference to FIGS. 19 and 20. First,the configuration of the common electrode substrate and the liquidcrystal display device having it according to the second embodiment willbe described with reference to FIG. 19. The entire configuration of theliquid crystal display device is the same as in the first embodimentshown in FIG. 12, and hence, will not be described. FIG. 19 is a planview showing a one-pixel configuration of the common electrode substrateand the liquid crystal display device having it according to the secondembodiment. The components in FIG. 19 having the same functions as thecorresponding components in FIG. 13 are given the same reference symbolsas the latter and will not be described below.

[0078] On the common electrode substrate 34, a red color filter R isformed in the region between straight lines α and β. A green colorfilter G is formed in the region on the right of the straight line α,and a blue color filter B is formed on the left of the straight line β(see FIG. 19). Resin double-layer portions 50 in which two or morelayers of color filter forming materials are laminated one on anotherand that are hence thicker than that part of the color filter which isopposed to the pixel electrode 16 are formed in those parts of theregions opposed to the regions between the drain bus lines 42 and thepixel electrode 16, which exclude the normal alignment regions where theauxiliary protrusions 10 are formed.

[0079] Next, the states of liquid crystal molecules in the commonelectrode substrate and in the liquid crystal display device having thesubstrate according to the second embodiment will be described withreference to FIG. 20. FIG. 20 is a simplified sectional view taken alongline F-F in FIG. 19 and shows pixel C in FIG. 26. The drain bus line 42on the left side is formed on the array substrate 32, and the pixelelectrode 16 is formed on the right side on the array substrate 32 (seeFIG. 20). On the other hand, on the common electrode substrate 34, thelight shield film 6 is formed in the region other than the region thatis opposed to the pixel electrode 16. The color filters R and B areformed on the common electrode substrate 34. The color filters B and Rare formed in an overlap state in the resin double-layer portion 50,whereby a step is formed in the region that is opposed to the regionbetween the pixel electrode 16 and the drain bus line 42. The commonelectrode 24 is formed on the color filters R and B and the elevatedportion that is formed by the color filters R and B, whereby aconductive protrusion is formed.

[0080] Broken lines in FIG. 20 indicate electric fields E₁, E₂, and E₄that develop between the electrodes. Influenced by the step of thecommon electrode 24, the strong, oblique electric field E₄ develops inthe vicinity of the end portion of the pixel electrode 16. Therefore,liquid crystal molecules in the vicinity of the end portion of the pixelelectrode 16 are inclined rightward in FIG. 20 unlike the correspondingliquid crystal molecules shown in FIG. 5, and are aligned in the samemanner as the liquid crystal molecules in the vicinity of the endportion of the pixel electrode 16 of pixel A shown in FIG. 4.

[0081] According to the second embodiment, liquid crystal molecules inthe vicinity of the end portions of the pixel electrode 16 can bealignment-restricted by the strong, oblique electric fields that developdue to the influence by the steps formed in the regions opposed to theregions between the pixel electrode 16 and the drain bus line 42.Therefore, the vertical crosstalk that would otherwise occur due to thepresence of the alignment defective regions 56 occurring in the regionsof the end portions of the pixel electrode 16 can be prevented. Sincethe areas of the alignment defective regions 56 decrease, the overlapwidth of the overlap regions 18 can be decreased, and hence, the paneltransmittance can be increased.

[0082] The invention is not limited to the above embodiments and variousmodifications are possible.

[0083] In the first embodiment, the light shield film 6 has the overlapregions 18. And, in the modification of the first embodiment, the lightshield film 6 has the overlap regions 18, and the light shield film 6 isformed outside the drain bus lines 42 between in the regions where theauxiliary protrusions 10 are formed. However, the invention is notlimited to those cases. For example, only the measure of forming thelight shield film 6 outside the drain bus lines 42 in between in theregions where the auxiliary protrusions 10 are formed may be taken.Since no liquid crystal alignment defect occurs in the regions where theauxiliary protrusions 10 are formed, the panel transmittance can beincreased without deteriorating the vertical crosstalk.

[0084] In the second embodiment, the steps, that is, the resindouble-layer portions 50 are formed by laminating color filter formingmaterials one on another. However, the invention is not limited to sucha case. Steps may be formed by using another resin such as a blackresin.

[0085] Although in the above embodiments, the light shield film 6 ismade of a metal such as Cr, the invention is not limited to such a case.The light shield film 6 may be formed by laminating the color filterforming materials one on another.

[0086] As described above, the invention can realize a common electrodesubstrate capable of providing high luminance and good displaycharacteristics as well as a liquid crystal display device having such acommon electrode substrate.

What is claimed is:
 1. A common electrode substrate comprising: atransparent insulating substrate to be arranged opposite to an arraysubstrate having pixel electrodes formed in respective pixel regionsthat are defined by a plurality of gate bus lines and drain bus lines,and to hold a liquid crystal having negative dielectric anisotropy; acommon electrode formed on the transparent insulating substrate;alignment regulating structures having linear protrusions formed on thecommon electrode; and a light shield film formed on the transparentinsulating substrate and having overlap regions that overlap the pixelelectrodes when viewed in a direction perpendicular to a surface of thetransparent insulating substrate so as to shield, from light, alignmentdefective regions of the liquid crystal formed in regions of endportions of the pixel electrodes.
 2. The common electrode substrateaccording to claim 1, wherein the light shield film has the overlapregions extending along the drain bus lines, when viewed in thedirection perpendicular to the surface of the transparent insulatingsubstrate.
 3. The common electrode substrate according to claim 2,wherein a width of the overlap regions is greater than or equal to 2 μmand smaller than or equal to 12 μm when viewed in the directionperpendicular to the surface of the transparent insulating substrate. 4.The common electrode substrate according to claim 1, wherein: thealignment regulating structures further have auxiliary protrusions thatbranch off the linear protrusions and extend along portions of the drainbus lines that are opposed to end portions of the pixel electrodes; andthe light shield film has the overlap regions in regions where theauxiliary protrusions are not formed, when viewed in the directionperpendicular to the surface of the transparent insulating substrate. 5.The common electrode substrate according to claim 1, wherein the lightshield film is formed outside each of the pixel electrodes in normalalignment regions other than the alignment defective regions of theliquid crystal, when viewed in the direction perpendicular to thesurface of the transparent insulating substrate.
 6. The common electrodesubstrate according to claim 5, wherein the light shield film is formedoutside each of the pixel electrodes so as to extend along the drain buslines, when viewed in the direction perpendicular to the surface of thetransparent insulating substrate.
 7. The common electrode substrateaccording to claim 6, wherein a distance between end portions of thelight shield film and end portions of each of the pixel electrodes inthe normal alignment regions of the liquid crystal is smaller than orequal to 7 μm, when viewed parallel with the surface of the transparentinsulating substrate.
 8. The common electrode substrate according toclaim 5, wherein: the alignment regulating structures further haveauxiliary protrusions that branch off the protrusions and extend alongportions of the drain bus lines that are opposed to end portions of thepixel electrodes; and the light shield film is formed outside each ofthe pixel electrodes in regions where the auxiliary protrusions areformed when viewed in the direction perpendicular to the surface of thetransparent insulating substrate.
 9. A common electrode substratecomprising: a transparent insulating substrate to be arranged oppositeto an array substrate having pixel electrodes formed in respective pixelregions that are defined by a plurality of gate bus lines and drain buslines, and to hold a liquid crystal having negative dielectricanisotropy; a common electrode formed on the transparent insulatingsubstrate; alignment regulating structures having linear protrusionsformed on the common electrode; and a light shield film formed on thetransparent insulating substrate outside each of the pixel electrodes innormal alignment regions other than alignment defective regions of theliquid crystal when viewed in a direction perpendicular to a surface ofthe transparent insulating substrate.
 10. The common electrode substrateaccording to claim 9, wherein the light shield film is formed outsideeach of the pixel electrodes so as to extend along the drain bus lineswhen viewed in the direction perpendicular to the surface of thetransparent insulating substrate.
 11. The common electrode substrateaccording to claim 9, wherein: the alignment regulating structuresfurther have auxiliary protrusions that branch off the linearprotrusions and extend along portions of the drain bus lines that areopposed to end portions of the pixel electrodes; and the light shieldfilm is formed outside each of the pixel electrodes in regions where theauxiliary protrusions are formed when viewed in the directionperpendicular to the surface of the transparent insulating substrate.12. The common electrode substrate according to claim 1, wherein thelight shield film is formed by laminating, one on another, formingmaterials of color filters that are formed in the respective pixelregions.
 13. A common electrode substrate comprising: a transparentinsulating substrate to be arranged opposite to an array substratehaving pixel electrodes formed in respective pixel regions that aredefined by a plurality of gate bus lines and drain bus lines, and tohold a liquid crystal having negative dielectric anisotropy; a commonelectrode formed on the transparent insulating substrate and havingsteps for alignment-restricting the liquid crystal in regions opposed toregions between each of the pixel electrodes and the drain bus lines;and alignment regulating structures having linear protrusions formed onthe common electrode.
 14. The common electrode substrate according toclaim 13, wherein the steps are formed thicker than the regions that areopposed to the respective pixel electrodes.
 15. The common electrodesubstrate according to claim 13, wherein: the alignment regulatingstructures further have auxiliary protrusions that branch off the linearprotrusions and extend along portions of the drain bus lines that areopposed to end portions of the pixel electrodes; and the steps areformed in regions where the auxiliary protrusions are not formed. 16.The common electrode substrate according to claim 13, wherein each ofthe steps is formed in such a manner that a resin is formed under thecommon electrode.
 17. The common electrode substrate according to claim16, wherein each of the steps is formed in such a manner that formingmaterials of color filters formed in the respective pixel regions arelaminated one on another.
 18. The common electrode substrate accordingto claim 16, wherein each of the steps is made of a black resin.
 19. Thecommon electrode substrate according to claim 1, wherein the linearprotrusions are formed obliquely with respect to edges of the pixelelectrodes.
 20. A liquid crystal display device comprising an arraysubstrate having pixel electrodes formed in respective pixel regionsthat are defined by a plurality of gate bus lines and drain bus lines,an opposite substrate arranged opposite to the array substrate, and aliquid crystal having negative dielectric anisotropy sealed between thearray substrate and the opposite substrate; wherein the oppositesubstrate is the common electrode substrate as set forth in claim 1.